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Differentiation of smooth muscle phenotypes in mouse mesangial cells
1Department of Clinical Bio-Regulatory Science, Faculty of Medicine, Kyoto University, Japan.
Abstract:
Smooth muscle alpha-actin (SMA) mRNA, a marker of vascular smooth muscle cells, was identified in the normal glomerular mesangium both in vivo and in vitro. Several populations of mesangial cells were studied to determine if SMA and basement membrane collagen were regulated together. The levels of SMA expression, which could be linked to the stage of differentiation, were different for the differing cell populations. One cell population had high SMA and type IV collagen levels at its early passages. The others expressed both interstitial and basement membrane collagens. The first population developed these phenotypic features at later passages. The levels of SMA and alpha 1(IV) collagen expression were regulated together in concert, whereas the alpha 2(I) collagen levels were expressed inversely to SMA and alpha 1(IV) collagen. Both SMA and type IV collagen were controlled by the methylation states of the cis-regulators; however, type I collagen was mainly regulated by the trans-acting regulators. Treatment with 5-azacytidine converted the cells of a fibroblast-phenotype to a smooth muscle cell-like phenotype. These cell lines may be useful for studying the differentiation process in vitro.
Insights
Smooth muscle alpha-actin (SMA) and type IV collagen are co-regulated during mesangial cell differentiation. Methylation controls SMA and type IV collagen, while trans-acting regulators control type I collagen.
Area of Science:
- Cell Biology
- Molecular Biology
- Nephrology
Background:
- Smooth muscle alpha-actin (SMA) mRNA marks vascular smooth muscle cells and is found in the glomerular mesangium.
- Mesangial cells exhibit diverse phenotypes, influencing their differentiation and extracellular matrix production.
Purpose of the Study:
- To investigate the co-regulation of SMA and basement membrane collagen in different mesangial cell populations.
- To explore the regulatory mechanisms, including methylation and trans-acting factors, controlling collagen expression in mesangial cells.
Main Methods:
- Analysis of SMA and collagen expression in various mesangial cell populations at different passages.
- Investigating the role of DNA methylation and trans-acting factors in regulating gene expression.
- Treatment with 5-azacytidine to induce phenotypic changes in fibroblast-like cells.
Main Results:
- Mesangial cell populations displayed distinct levels of SMA and collagen expression, correlating with differentiation stage.
- SMA and alpha 1(IV) collagen expression were coordinately regulated, while alpha 2(I) collagen expression was inversely correlated.
- Methylation of cis-regulators controlled SMA and type IV collagen, whereas trans-acting regulators controlled type I collagen.
Conclusions:
- SMA and type IV collagen expression are tightly regulated together during mesangial cell differentiation.
- Epigenetic modifications (methylation) and trans-acting factors play distinct roles in regulating collagen types.
- 5-azacytidine treatment can induce a smooth muscle cell-like phenotype, suggesting potential for studying differentiation in vitro.